For the start of this year's hurricane season next week, the GFS model (Figure 2) is forecasting that there will be strong upper-level winds over the Gulf of Mexico. These winds are part of the so-called Subtropical jet stream. The jet stream--the band of high velocity winds that circles the globe--always has at least one branch, the polar jet. As its name implies, the polar jet lies close to the pole, and circles it entirely. Sometimes the jet splits, and a branch called the Subtropical jet blows across subtropical latitudes, where the Gulf of Mexico lies. As we can see from the GFS forecast for June 3 in Figure 2, both the polar and subtropical jets are apparent where the color coding indicates strong winds at the 300 millibar level (the jet stream occurs at an altitude in the atmosphere where the pressure ranges between 300 mb and 200 mb). The strong winds of the Subtropical jet will create too much wind shear for a tropical storm to form in the Gulf of Mexico next week, and the jet is expected to remain strong for at least the next two weeks. So, an early start to hurricane season looks unlikely this year.
Figure 2. GFS forecast for June 3 2006 at 300 millibars, the altitude where the jet stream is found. The polar and subtropical branches of the jet stream are clearly visible where upper-level wind speeds are highest. An area of light upper level winds and low wind shear is forecast to develop over the southern Caribbean Sea.
What about the southern Caribbean Sea, where the GFS model is predicting very light upper level winds, and where wind shear is likely to be low? Well, we will have to watch this area for tropical storm formation, but as I indicated before, the tropical waves one needs to act as the seed for a storm are usually too far south in June. Tropical waves usually do not start entering the Caribbean until July.
Here a link to his blog....
http://www.wunderground.com/blog/JeffMasters/show.html
FEEL FREE TO LEAVE COMMENTS!CHRISTY
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